Re: [PATCH 1/7] rust: kunit: support KUnit-mapped `assert!` macros in `#[test]`s

David Gow
2025-05-05T06:02:16Z

[-- Attachment #1: Type: text/plain, Size: 7366 bytes --]

On Sat, 3 May 2025 at 05:51, Miguel Ojeda <ojeda@kernel.org> wrote:
>
> The KUnit `#[test]` support that landed recently is very basic and does
> not map the `assert*!` macros into KUnit like the doctests do, so they
> panic at the moment.
>
> Thus implement the custom mapping in a similar way to doctests, reusing
> the infrastructure there.
>
> In Rust 1.88.0, the `file()` method in `Span` may be stable [1]. However,
> it was changed recently (from `SourceFile`), so we need to do something
> different in previous versions. Thus create a helper for it and use it
> to get the path.
>
> With this, a failing test suite like:
>
> #[kunit_tests(my_test_suite)]
> mod tests {
> use super::*;
>
> #[test]
> fn my_first_test() {
> assert_eq!(42, 43);
> }
>
> #[test]
> fn my_second_test() {
> assert!(42 >= 43);
> }
> }
>
> will properly map back to KUnit, printing something like:
>
> [ 1.924325] KTAP version 1
> [ 1.924421] # Subtest: my_test_suite
> [ 1.924506] # speed: normal
> [ 1.924525] 1..2
> [ 1.926385] # my_first_test: ASSERTION FAILED at rust/kernel/lib.rs:251
> [ 1.926385] Expected 42 == 43 to be true, but is false
> [ 1.928026] # my_first_test.speed: normal
> [ 1.928075] not ok 1 my_first_test
> [ 1.928723] # my_second_test: ASSERTION FAILED at rust/kernel/lib.rs:256
> [ 1.928723] Expected 42 >= 43 to be true, but is false
> [ 1.929834] # my_second_test.speed: normal
> [ 1.929868] not ok 2 my_second_test
> [ 1.930032] # my_test_suite: pass:0 fail:2 skip:0 total:2
> [ 1.930153] # Totals: pass:0 fail:2 skip:0 total
>
> Link: https://github.com/rust-lang/rust/pull/140514 [1]
> Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
> ---

Nice! While I do think there may still be some cases where we might
want to use KUnit-specific macros in the future (particularly if we
have more complex, multithreaded test contexts), this is definitely
better for most cases.

I also managed to test it against the 1.88 nightly, and the message is
looking good.

Reviewed-by: David Gow <davidgow@google.com>

Cheers,
-- David

> init/Kconfig | 3 +++
> rust/Makefile | 3 ++-
> rust/kernel/kunit.rs | 1 -
> rust/macros/helpers.rs | 16 ++++++++++++++++
> rust/macros/kunit.rs | 28 +++++++++++++++++++++++++++-
> rust/macros/lib.rs | 4 ++++
> 6 files changed, 52 insertions(+), 3 deletions(-)
>
> diff --git a/init/Kconfig b/init/Kconfig
> index 63f5974b9fa6..5f442c64c47b 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -140,6 +140,9 @@ config LD_CAN_USE_KEEP_IN_OVERLAY
> config RUSTC_HAS_COERCE_POINTEE
> def_bool RUSTC_VERSION >= 108400
>
> +config RUSTC_HAS_SPAN_FILE
> + def_bool RUSTC_VERSION >= 108800
> +
> config PAHOLE_VERSION
> int
> default $(shell,$(srctree)/scripts/pahole-version.sh $(PAHOLE))
> diff --git a/rust/Makefile b/rust/Makefile
> index 3aca903a7d08..075b38a24997 100644
> --- a/rust/Makefile
> +++ b/rust/Makefile
> @@ -402,7 +402,8 @@ quiet_cmd_rustc_procmacro = $(RUSTC_OR_CLIPPY_QUIET) P $@
> -Clink-args='$(call escsq,$(KBUILD_PROCMACROLDFLAGS))' \
> --emit=dep-info=$(depfile) --emit=link=$@ --extern proc_macro \
> --crate-type proc-macro \
> - --crate-name $(patsubst lib%.$(libmacros_extension),%,$(notdir $@)) $<
> + --crate-name $(patsubst lib%.$(libmacros_extension),%,$(notdir $@)) \
> + @$(objtree)/include/generated/rustc_cfg $<
>
> # Procedural macros can only be used with the `rustc` that compiled it.
> $(obj)/$(libmacros_name): $(src)/macros/lib.rs FORCE
> diff --git a/rust/kernel/kunit.rs b/rust/kernel/kunit.rs
> index 1604fb6a5b1b..2659895d4c5d 100644
> --- a/rust/kernel/kunit.rs
> +++ b/rust/kernel/kunit.rs
> @@ -323,7 +323,6 @@ mod tests {
>
> #[test]
> fn rust_test_kunit_example_test() {
> - #![expect(clippy::eq_op)]
> assert_eq!(1 + 1, 2);
> }
>
> diff --git a/rust/macros/helpers.rs b/rust/macros/helpers.rs
> index a3ee27e29a6f..57c3b0f0c194 100644
> --- a/rust/macros/helpers.rs
> +++ b/rust/macros/helpers.rs
> @@ -86,3 +86,19 @@ pub(crate) fn function_name(input: TokenStream) -> Option<Ident> {
> }
> None
> }
> +
> +pub(crate) fn file() -> String {
> + #[cfg(not(CONFIG_RUSTC_HAS_SPAN_FILE))]
> + {
> + proc_macro::Span::call_site()
> + .source_file()
> + .path()
> + .to_string_lossy()
> + .into_owned()
> + }
> +
> + #[cfg(CONFIG_RUSTC_HAS_SPAN_FILE)]
> + {
> + proc_macro::Span::call_site().file()
> + }
> +}
> diff --git a/rust/macros/kunit.rs b/rust/macros/kunit.rs
> index 4f553ecf40c0..eb4f2afdbe43 100644
> --- a/rust/macros/kunit.rs
> +++ b/rust/macros/kunit.rs
> @@ -101,6 +101,8 @@ pub(crate) fn kunit_tests(attr: TokenStream, ts: TokenStream) -> TokenStream {
> // ```
> let mut kunit_macros = "".to_owned();
> let mut test_cases = "".to_owned();
> + let mut assert_macros = "".to_owned();
> + let path = crate::helpers::file();
> for test in &tests {
> let kunit_wrapper_fn_name = format!("kunit_rust_wrapper_{}", test);
> let kunit_wrapper = format!(
> @@ -114,6 +116,27 @@ pub(crate) fn kunit_tests(attr: TokenStream, ts: TokenStream) -> TokenStream {
> test, kunit_wrapper_fn_name
> )
> .unwrap();
> + writeln!(
> + assert_macros,
> + r#"
> +/// Overrides the usual [`assert!`] macro with one that calls KUnit instead.
> +#[allow(unused)]
> +macro_rules! assert {{
> + ($cond:expr $(,)?) => {{{{
> + kernel::kunit_assert!("{test}", "{path}", 0, $cond);
> + }}}}
> +}}
> +
> +/// Overrides the usual [`assert_eq!`] macro with one that calls KUnit instead.
> +#[allow(unused)]
> +macro_rules! assert_eq {{
> + ($left:expr, $right:expr $(,)?) => {{{{
> + kernel::kunit_assert_eq!("{test}", "{path}", 0, $left, $right);
> + }}}}
> +}}
> + "#
> + )
> + .unwrap();
> }
>
> writeln!(kunit_macros).unwrap();
> @@ -152,7 +175,10 @@ pub(crate) fn kunit_tests(attr: TokenStream, ts: TokenStream) -> TokenStream {
> }
> }
>
> - let mut new_body = TokenStream::from_iter(new_body);
> + let body = new_body;
> + let mut new_body = TokenStream::new();
> + new_body.extend::<TokenStream>(assert_macros.parse().unwrap());
> + new_body.extend(body);
> new_body.extend::<TokenStream>(kunit_macros.parse().unwrap());
>
> tokens.push(TokenTree::Group(Group::new(Delimiter::Brace, new_body)));
> diff --git a/rust/macros/lib.rs b/rust/macros/lib.rs
> index 9acaa68c974e..8bd7906276be 100644
> --- a/rust/macros/lib.rs
> +++ b/rust/macros/lib.rs
> @@ -6,6 +6,10 @@
> // and thus add a dependency on `include/config/RUSTC_VERSION_TEXT`, which is
> // touched by Kconfig when the version string from the compiler changes.
>
> +// TODO: check that when Rust 1.88.0 is released, this would be enough:
> +// #![cfg_attr(not(CONFIG_RUSTC_HAS_SPAN_FILE), feature(proc_macro_span))]
> +#![feature(proc_macro_span)]
> +
> #[macro_use]
> mod quote;
> mod concat_idents;
> --
> 2.49.0
>

[-- Attachment #2: S/MIME Cryptographic Signature --]
[-- Type: application/pkcs7-signature, Size: 5281 bytes --]